Sun 3/280 freezes

[Mark Smith]

We have a SUN 3/280, with 24 Megabytes of main memory, 3 ALM-II cards, a
second ethernet, 1600/6250 tape drive and 2 xylogics 7053 controllers,
with 2 drives on each controller.  Every once in a while, for no apparent
reason the system will freeze.  The only way to get it to continue is
break on the console and reboot.

By 'freeze' I mean - no disk activity, no i/o to any serial ports, no
network response, no response to anything but break on the keyboard.  The
status lights on the cpu card are still moving, but very slowly.

We're running SUN OS 4.0.3 with the patches to update ufs_bmap.o

Does anybody have any ideas what could be causing this - or good ways to
go about diagnosing it?

Thanks

Mark Smith
mjs at virginia.edu
Univeristy of Virginia
Computer Science Department